The fuel cycle - performance of the first charge fuel and the way forward

Sizewell B is the UK's first commercial pressurised water reactor and was first taken critical on 31st January 1995. The core is rated nominally at 3411 MW (thermal) and for the first cycle was capable of delivering 384 effective full power days (EFPDS) of output. This design was 'first charge specific' and was intended to satisfy the commissioning and power ascension phases, and then an operational full power run of approximately 10 months to the first refuelling outage. The intent was that this should establish a foundation for establishing a 12 month cycle which included the duration of the annual outage. On 28th June 1996 the reactor was shut down for the first refuelling outage after achieving a nominal burn-up of 378 EFPDs. During the 55 day refuelling outage, 84 of the 193 fuel assemblies were replaced. The core design for cycle 2 is capable of generating 386 EFPDs for 3411 MW (thermal) full power. This cycle is the start of a transition from 12 month to 18 month cycles and necessitates the use of higher enrichment fuel than for cycle 1. This paper reviews the first year fuel performance, the refuelling process and the enhancements made for future operations.